WinForms ScrollableControl's scrollbars capture mouse wheel? - c#

I have a custom ZoomBox control based on ScrollableControl which controls its scrollbars through AutoscrollMinSize property.
I would like to be able to handle WM_MOUSEWHEEL events to adjust control's Zoom.
I made necessary steps to make sure that the control receives the mouse events even when it is not in focus, by filtering them on the parent form.
It seems though that the events only reach the OnMouseWheel method if the control does not have its scrollbars active. If it does, it appears that the mousewheel events are being redirected to the scrollbars which handle them (by scrolling).
I would like the scrollbars to be there but only be controlled in a "traditional way", i.e. by dragging the slider or clicking on arrows etc. and handle the wheel myself. Is it possible to achieve that?

Inherit from the ScrollableControl in question and override OnMouseWheel(). In that method don't call base.OnMouseWheel().
As far as I can tell there's no other way to stop ScrollableControl from scrolling if the scroll bars are present.
A side effect is that you will no longer get MouseWheel events. Fixing that is another question. Conceptually you want to call base.base.OnMouseWheel().

Related

MouseWheel event doesn't fire on a non-Selectable Control

I have written a custom Control, based on other code, which includes a call to SetStyle(ControlStyles.Selectable, false);
This prevents the following code from being called (which works if I remove the above line and click on the Control first to 'focus' it):
protected override void OnMouseWheel(MouseEventArgs e)
{
ScrollBar.Value = Math.Min(ScrollBar.Value - e.Delta, ScrollBar.Maximum - ScrollBar.LargeChange);
LayoutChanged();
}
My control does not need focus so Selectable=false is correct.
What do I need to do so that I can run this code whenever the mouse is over my control and the MouseWheel is moved regardless of where the focus is?
Thanks for the comments. A additional info:-
I am running Windows 7 but any solution must work on any OS.
The Control is inherited via Control/ControlBase/BaseControl/BaseStyleControl where the latter 3 are DevExpress controls.
The real focus should not be changed just because the cursor hovers over my control
There are no child controls other than a scrollbar (an inherited DevExpress one) which is normally invisible and shows itself when the mouse hovers over where it would be when visible.
The control does nothing but draw itself (imagine a number of bookshelves one under the other with book covers drawn on them - the number of shelves increases to accommodate all the books and the scrollbar allows all to be scrolled into view.
Since this is a use-anywhere Control, getting MouseWheel events from a Parent that knows about its requirements isn't a good idea.
Maybe there is a way of registering for a first-look (is that a MessagePreview?) to pinch MouseWheel events before normal processing happens.

Events for the border of a form?

I want to know when the user has the mouse over the border of a form. I also want to be able to know if its the top/bottom or left/right border.
There does not seem to be any events for this. I have tried using MouseMove on the form but it only fires when it is "inside" the form.
I have tried looking at the Bounds property but that does not have any events.
What can I do to solve this?
You have to override the WNDPROC method and look for WM_NC* messages.
This link should get you started: Mouse events from a non-client area of a control

How to fix scrollbars when the window or container is resized?

Currently in my application I am using the HScrollBar and VScrollBar for panning around in a large image. The part of the image that is shown is based on the scrollbar's Value property. However, when resizing the SplitContainer or resizing the form window the scrollbar's Value does not automatically update and it may render something off-screen.
At this point I noticed that if you clicked the scrollbar's arrow it magically fixes the scrollbar. I was wondering if there was any way to simulate clicking the scrollbar to do this in the Form_Resize and SplitContainer_Resize event handlers but I couldn't find anything.
Having to manually adjust the scrollbar's value in all resizing events is slow, ugly, and doesn't work well. I'd really like for the scrollbar to just automatically fix itself when the window resizes like it does when you click its arrow but I'm not sure how.
Try calling the scrollbar's Invalidate() method in the form's resize event handler:
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.invalidate.aspx
That should cause it to redraw correctly after the form is resized.
Use something like this:
HScrollBarObject.SetStyle(ControlStyles.ResizeRedraw, true);

How can I cause anchored child controls to resize themselves?

C#. I'm filling a panel with controls such that a scrollbar comes up. When the scrollbar shows up, I would like the controls (anchored top|left|right) to resize so they aren't covered by the scrollbar. If I make the form bigger and then smaller again, they resize properly, but I don't know how to make them do this sizing when the scrollbar shows up.
There doesn't seem to be an event for this. However, you could override the form's virtual AdjustFormScrollbars method in order to detect if a change has occurred.

In a WPF ListView how can I prevent auto scrolling?

I have a WPF ListView which currently scrolls everytime I click on an item which is only partially visible. How can I keep the control from scrolling that item into view (instead simply selecting the partially visible one)? This behavior is very annoying when doing a drag from this control.
Thanks.
Added: I am looking for a solution to keep the control itself from scrolling when contents are clicked that the control believes are not fully visible. Often this is by a few pixels and the scroll is not necessary.
The items scroll into view because the default behavior on list item click is to call BringIntoView(). You can add an event handler for the RequestBringIntoView event and catch it before it bubbles up from the ListViewItems to the ScrollViewer. In your handler, check the bounds of the sender against the visible region and if you decide that you don't need to scroll, set the event's Handled flag to true.
Since I'm currently on the road, I cannot try this, but have you tried playing around with CanContentScroll, and/or wrapping the scrollable content into a Panel, as suggested by the ScrollViewer Overview on MSDN?
In the worst case, you might want to replace the ListView's ItemsPanel by a hacked ScrollViewer with a "fuzz" factor, e.g. by capturing the RequestBringIntoView event.
have you tried this approach?
just as an addon, I don't know how much you know about the subject, but here is a good place to read more about it.
added:
I just found that you can prevent the mouse wheel of scrolling as well.

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